This invention relates generally to irrigation and sprinkling systems, and more particularly to control systems in which periodic, automatic watering is enabled or disabled by ground moisture sensors.
Automatic irrigation or sprinkling systems are often utilized in commercial environments such as golf courses or public parks to alleviate manual watering and to control the time and amount of watering for a particular area. These automatic watering systems generally comprise an irrigation clock which initiates sprinkling at predetermined times for predetermined intervals.
A disadvantage of systems utilizing preset clocks or timers is that the watering system is automatically turned on regardless of soil moisture or weather conditions. As a result, excess watering can occur during periods of abnormal rainfall or rain occurring during the watering cycle.
Rather than relying on manual intervention to override the automatic timers, ground moisture sensors have been employed to inhibit watering when the level of moisture is at or above a chosen value. As a result, automatic watering can be accomplished without the inherent problem of overwatering.
The override feature provided by the ground moisture sensors, however, presents another problem. At certain times, for example during periods of unusual heat or drying conditions, watering may be necessary even though the ground sensors provide an opposite indication. On golf courses, for example, the grass is cut very close to the ground on the fairway and especially on the putting green. On a very hot day, the superficial layer of the soil will dry more rapidly than the underlying soil. The sensor, generally positioned to measure the moisture in the underlying soil, may inhibit the sprinkling system even though watering may be required to prevent certain areas from drying out or burning. It would be desirable, under these conditions, to permit watering for just a short period to moisten the superficial ground level and prevent damage to the green or fairway. However, this would require that the ground moisture sensor be manually disabled to allow the sprinklers to be turned on.
The present invention overcomes this disadvantage by providing a system which can bypass the ground moisture sensor and enable watering when watering or irrigation would normally be disabled by the sensor. The present invention includes a central irrigation clock programmed to enable watering of several zones of an area under irrigation control. To reduce the burden on the water supply and to maintain adequate pressure, the zones can be watered sequentially with each zone being watered for a given time period.
Located in proximity to the clock at a central office is a remote control transmitter. The remote control transmitter, in response to the activation of a bypass switch or closure of a bypass contact, will transmit a direct current bypass signal to remote receivers which effectively latch or hold that signal. The remote control transmitter will then transmit alternating current to the remote receiver to permit watering regardless of the state of the central clock.
Located within each zone is a valve installed in an irrigation line to control water flow to a sprinkler head. Located in proximity to the valve is a remote receiver connected to a ground moisture sensor that is in turn connected to the valve. Power is delivered through the receiver and the sensor to the valve during normal operation. The remote receiver is also directly connected to the valve to deliver power and open the valve during a bypass mode of operation. Each remote receiver is connected to the centrally located remote transmitter by a two-wire power line which delivers both ac power and the dc bypass signal.
The present invention provides a simple, easy to install, and inexpensive to manufacture system in which remotely located ground sensors can be effectively bypassed from a central office. The advantages of the present invention are realized with a minimum of amount of circuitry and minimum wiring between a central office and remotely located valves.